.father{
  width: 300px;
  height: 300px;
  background-color: aquamarine;
  .son1{
    width: 150px;
    height: 150px;
    background-color: bisque;
    .sun1{  
      width: 100px; 
      height: 100px;
      background-color: pink;
    }
  }
  .son2{
    width: 50px;
    height: 50px;
    background-color: rgb(0, 106, 255);
  }
}